Unique fluorescence properties of a cyanobacterium Gloeobacter violaceus PCC 7421: reasons for absence of the long-wavelength PSI Chl a fluorescence at -196 degrees C.

We investigated the reason for the absence of the long-wavelength PSI Chl a fluorescence at -196 degrees C in the cyanobacterium Gloeobacter violaceus using two methods: p-nitrothiophenol (p-NTP) treatment and time-resolved fluorescence spectra. The p-NTP treatment showed that PSII Chl a fluorescence was specifically affected in a manner similar to that for Synechocystis sp. PCC 6803 and spinach chloroplasts, although there were no components modified by the p-NTP treatment, indicating an absence of the long-wavelength PSI Chl a fluorescence.